A device referred to as an opto-isolator (also referred to as an optical isolator, optocoupler and photocoupler) is often used to reduce noise and prevent other deleterious effects in electrical circuits. For example, at least some of the electronic noise typically derives from back end digital signal processing which is deleterious to the performance of analog integrated circuits. In addition, an opto-isolator is often used to reduce ground loops and ground noise spikes in electronic circuitry; and to isolate circuitry due to incompatible, dangerous, or otherwise deleterious voltage regimes, such as to isolate high voltage networks from low voltage electronics. Thus, opto-isolators are used for various reasons in modern electronic circuit design.
Opto-isolators electrically isolate portions of a circuit thereby reducing noise. An opto-isolator uses a short optical transmission path to transfer a signal between elements of a circuit, typically a LED and an optical receiver, while keeping them electrically isolated. The LED and optical receiver are separated so that light may travel across a barrier but electrical current may not. When an electrical signal is applied to the input of the opto-isolator, the LED generates a light signal, and an optical receiver generates a corresponding electrical signal as the output. When a photodiode is used as the optical receiver, the output current is proportional to the amount of incident light supplied by the LED. The ratio of the amount of current output by the photodiode to the amount of current input to the LED is referred to as the current transfer ratio.
Conventional embodiments utilizing LEDs have been limited, however, to low speed opto-isolation applications because they are limited by the response time of the LED. These conventional embodiments have also been limited in their current transfer ratio due to high power dissipation of LED emitters. Moreover, conventional embodiments have been bulky and prone to optical misalignment of the optical emitter and optical receiver. The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate an example of technology areas where some embodiments may be practiced.